The present invention relates to pliers, and more particularly to a release mechanism for locking pliers.
Basically two types of locking pliers are available on the market. One type is self-adjusting or auto-adjusting locking pliers which have jaws that are self-adjusting according to the size of the workpiece to be grasped between the jaws, and the second type are locking pliers which do not incorporate self-adjusting capabilities. An example of self-adjusting locking pliers are disclosed in U.S. Pat. No. 6,941,844, issued to the present inventor. There are many examples of locking pliers which do not incorporate self-adjusting capabilities. As just a couple of examples, this type of non-adjusting plier is disclosed in U.S. Pat. No. 5,056,385, a locking plier sold under the trademark “VISE-GRIP” and U.S. Pat. No. 6,227,080.
All such locking pliers, whether self-adjusting or not, incorporate an “over-center” or “past-dead-center” compound toggle locking mechanism or linkage whereby when the movable jaw of the plier is rotated to seize a workpiece firmly between the movable and the fixed jaw as the handles are tightly compressed, the toggle mechanism locks the jaws onto the workpiece with extreme pressure.
All of the prior art locking pliers have a shortcoming in regard to the release mechanism to release the jaws. This is so because the stationary assembly of the locking pliers, including the upper jaw, the main body and the upper handle, as a whole functions as a spring element when the pliers are locked. Accordingly, the entire energy of the locking mechanism is stored up in the upper stationary assembly or handle.
Most such locking pliers either employ a release lever which is tripped to unlock the jaws or the handles are simply pulled apart. Because of the high energy stored in the upper stationary assembly of the pliers under locked conditions, the lower movable handle when released flings outward with a significant force which can cause injuries. Accidental openings can also occur with unintentional contact with the release lever which is usually positioned on the inside of the lower movable handle. In addition, to release the locked jaws one must either trip a release lever, normally on the lower movable handle, or pull the handles apart, and in any event this normally requires the use of two hands. It is not appropriately or easily possible to release the locked jaws with one hand, being the same hand that is manipulating the pliers.